1. Field of the Invention
The present invention relates to a plasma display panel (PDP), and more particularly to a PDP that enhances illumination efficiency while reducing a discharge firing voltage.
2. Description of Related Art
One type of PDP is the triode surface-discharge PDP. The triode surface-discharge PDP includes a first substrate having an inner surface on which there are formed sustain electrodes and scan electrodes, and a second substrate opposing the first substrate with a predetermined gap therebetween and having an inner surface on which there are formed address electrodes. The first and second substrates are sealed together in a state where discharge gas is provided therebetween. Discharge of the PDP is affected by operation of the scan electrodes and the address electrodes, which are connected to each line and independently controlled. Sustain discharge is realized by the sustain electrodes and the scan electrodes.
The PDP utilizes glow discharge to generate visible light. Subsequent to the generation of glow discharge, the PDP undergoes a predetermined process before users can view images formed by the PDP. In particular, with the generation of glow discharge, gas plasma is generated that is excited by the collision of atoms with the gas, after which ultraviolet (UV) rays are emitted from the gas. The UV rays collide with phosphors in discharge cells such that the phosphors emit visible light. This visible light passes through the first substrate for users to view. During this process, however, significant loss of input power applied to the sustain electrodes and scan electrodes occurs.
This glow discharge occurs by applying between two electrodes a high voltage that exceeds the discharge firing voltage. Hence, a relatively high voltage is needed to initiate discharge. If discharge occurs, voltage distribution is distorted between cathodes and anodes as a result of a space charge effect, which is generated on the dielectric layer in the vicinity of cathodes and anodes. Formed between two electrodes are a cathode sheath region, which is located in the periphery of cathodes and wherein most of the voltage applied to two electrodes to effect discharge is consumed, an anode sheath region, which is located in the periphery of anodes and wherein part of the voltage is consumed, and a positive column region, which is located between the other two regions and wherein almost no voltage is consumed. In the cathode sheath region, electron heating efficiency is present in a secondary electron coefficient of an MgO protection layer formed on a surface of a dielectric layer, and in the positive column region, most of the input energy is consumed in electron heating.
Vacuum UV rays that emit visible light by colliding with phosphors are generated as xenon (Xe) gas changes from an excitation state to a ground state. The excitation state of xenon (Xe) occurs by collision between xenon (Xe) gas and electrons. Accordingly, to increase the amount of visible light generated relative to the input energy (i.e., illumination efficiency), electron heating efficiency must be raised to thereby increase collisions between xenon (Xe) gas and electrons.
In the cathode sheath region, although most of the input energy is consumed, the electron heating efficiency is low. In the positive column region, the electron heating efficiency is very high, even though the consumption of input energy is low. Accordingly, a high illumination efficiency is possible by increasing the positive column region (discharge gap).
Further, with respect to a ratio of electrons consumed among all electrons according to variations in a ratio (E/n) between an electric field (E) formed in the discharge gap (positive column region) and a gas density (n), in the same ratio (E/n), the electron consumption ratio increases in the sequence of xenon excitation (Xe*), xenon ions (Xe+), neon excitation (Ne*), and neon ions (Ne+). In addition, in the same ratio (E/n), the greater the increase in a partial pressure of xenon (Xe), the more the electron energy decreases. That is, if the electron energy decreases, the partial pressure of xenon (Xe) increases, and if the partial pressure of xenon (Xe) increases, among the electrons consumed in xenon excitation (Xe*), xenon ions (Xe+), neon excitation (Ne*), and neon ions (Ne+), the ratio of electrons consumed in the excitation of xenon (Xe) compared to other areas is increased. As a result, illumination efficiency is increased.
As described above, an increase in the positive column region results in an increase in electron heating efficiency. Further, an increase in xenon (Xe) partial pressure results in increasing a heating ratio of electrons consumed for xenon excitation (Xe*). Accordingly, increasing both of these factors results in enhancing electron heating efficiency such that illumination efficiency is improved.
However, increases in the positive column region and xenon (Xe) partial pressure result in an increase in a discharge firing voltage, as well as in manufacturing costs of the PDP.
Therefore, in order to enhance illumination efficiency, it is necessary that increases in the positive column region and xenon (Xe) partial pressure be realized while maintaining a low discharge firing voltage.
As is well known, when a length and pressure of the discharge gap are identical, the discharge firing voltage required when utilizing a surface discharge structure is less than that required when using an opposing discharge structure.